684123921 has 32 divisors (see below), whose sum is σ = 1093232000. Its totient is φ = 420323904.

The previous prime is 684123907. The next prime is 684123929. The reversal of 684123921 is 129321486.

It is not a de Polignac number, because 684123921 - 2⁶ = 684123857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (684123929) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 300375 + ... + 302643.

It is an arithmetic number, because the mean of its divisors is an integer number (34163500).

Almost surely, 2^684123921 is an apocalyptic number.

It is an amenable number.

684123921 is a deficient number, since it is larger than the sum of its proper divisors (409108079).

684123921 is a wasteful number, since it uses less digits than its factorization.

684123921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3150 (or 3144 counting only the distinct ones).

The product of its digits is 20736, while the sum is 36.

The square root of 684123921 is about 26155.7626728796. The cubic root of 684123921 is about 881.1400174197.

The spelling of 684123921 in words is "six hundred eighty-four million, one hundred twenty-three thousand, nine hundred twenty-one".